The present invention relates to a rock drill bit.
As well known in the art of down the hole drilling using percussive type drills, the removal of debris extracted from the ground by a drill bit is important. There are many different varieties of arrangements which provide the necessary removal of the debris. It is very important while drilling that the materials cut from within the drilling area are removed therefrom such that the drill bit surface has minimal wearing therefrom. Flow paths are commonly found on drill bits for the removal of the debris. If the debris is not flushed from the drilling area there is a good chance that the drill will lock and have to be extracted from the hole which causes expensive down time.
Some examples of these types of drill bits which include flow paths or flush channels are shown in U.S. Pat. No. 5,890,551 (Liljebrand et al.) which provides a drill bit with a particular arrangement of recesses and agitators. Also there is provided a flushing channel which is arranged to flush the debris from the drilling area. U.S. Pat. No. 5,358,063 (Hedlund et al.) shows a drill bit, very similar to that of the above mentioned Patent but differs in that there is disclosed a flushing channel with an increased cross sectional area in comparison to the above mentioned Patent of Liljebrand. U.S. Pat. No. 5,794,728 (Palmberg) also shows a very similar drill bit to that shown in Liljebrand but has an arrangement of flush grooves which carry a larger volume of debris.
U.S. Pat. No. 3,955,635 (Skidmore) shows a drill bit which has provides flush grooves which can remove an even larger volume of debris than provided in the above mentioned patents. There is however, no second channel is shown for extracting the debris through the main body of the Patent.
U.S. Pat. No. 5,025,875 (Witt) provides a drill bit with secondary flush channels which divert some of the air and water mixture flushed through the flush channels to the sides of the bit but does not disclose a secondary relief channel for flushing out the debris.
These above mentioned patents do not however provide a specific arrangement of channels designed for increased relief from the pressure of the debris being flushed by the air and water mixture.
According to the present invention there is provided a rock drill bit comprising:
a main body arranged to drill at the end of a shaft of the drilling assembly, the main body having a diameter larger than that of the shaft;
a front face on the main body arranged to engage an area for drilling;
an outer surface extending rearwards from the front face;
a flush channel extending through the main body to the front face;
at least one open end of the flush channel at the front face which is arranged to provide a mixture of air and water to an area at the front face;
a plurality of contact points on the front face for engaging the area;
a flush groove extends from the open end of the flush channel outwards to the outer surface; and,
at least one relief bore extending from the front face rearwards to a relief area behind the outer surface for providing a release for the mixture of air and water from the front face to the relief area;
the relief bore is located within the flush channel between the open end and the outer surface such that the debris is flushed from the drilling area to an area behind the main body.
Conveniently a conical joining portion is located between the main body and the shaft and increases in diameter from the shaft to the main body.
Conveniently the relief bore exits are the conical joining portion.
Preferably the relief bore is at an angle relative to the flush groove.
Preferably there is two relief bores.
Preferably there is two flush grooves each having a relief bore extending therefrom.
Preferably there is a plurality of recesses at an outer edge of the front face.
Conveniently the flush grooves go to a respective recess.
Preferably the relief bore exits the outer surface of the main body between two recesses.